My 4 year old had the surgery this summer when he was 3. The surgeon did not prepare me for what would ensue. The literature he gave me was inadequate. I only found out from another mother after the fact that I should have expected the hell we went through. It is described as the worst 2 weeks of your life.
It is a hard surgery with a painful recovery. There is bleeding and pain, lack of eating and drinking. My son would not take the pain medicine and we could not force it (3 nurses and I could not hold him down to get it in him at the ER). My son became dehydrated requiring a trip to the ER for an IV. About 6-7 days post op he'd wake up spitting blood and screaming in pain. I found out later this is fairly common.
I don't mean to scare you, I just want you to know what to expect and be prepared. Doing them both at the same time is probably good from the fear factor point of view for the children, but it will be hard on you to tend to both. Very cute ideas for helping them let you know what they need, though.
My son didn't recover for almost two weeks. The pamphlet they gave me made it all sound quick and easy and not much recovery time. It's a LIE! What I have heard from other moms is that it is just a hard two weeks and it's all to be expected.
Keep in touch with your surgeon and let them know what's going on. Call the night number if they are suffering or bleeding and you can't fix it. If they do bleed (which is normal to a point) you can put ice packs around their necks. It causes a reflex that will constrict the blood vessels and stop the bleeding. Occasionally they need to have their throats cauterized to reseal the wound. We did not have to do this.
Watch for signs of dehydration (infrequent or dark urine, dry lips, tearless crying, tenting skin, etc.) Keep track of what they eat and drink so you can have an accurate picture of whether they are dehydrated or not. Find out from your pediatrician what the minimum is that they can get by on for a day so you have a guide.
They will cycle through good days and bad. They may look like they are on the mend and then have a setback - this is normal. You may not have as bad an experience as we did, but you should be ready for all the possibilities especially with two. I hope it all goes so easy for you, but know there's a sympathetic mom out there if it doesn't. Best of luck. I'll say a prayer for you all.